Cake: Preheat oven to 350 degrees and spray baking dish with non-stick baking spray. In a bowl, sift all the dry ingredients together for the cake. The brown sugar, if packed, won't sift all the way - that's fine. In a separate bowl, mix all the wet ingredients for the cake, except the boiling water. Add the wet ingredients into the dry, and whisk well (or use a hand mixer or stand mixer). Once combined, add hot water, and mix until smooth. The batter will be fairly liquid. Pour into baking dish, and bake for 35-40 minutes, or until a toothpick comes out clean. For cupcakes (regular sized and oversized), bake for 20 minutes. Let cool completely before icing.

Chocolate Buttercream: In a bowl, melt chocolate chips in the microwave with milk. Microwave in 20-30 sec intervals, stirring each time the microwave stops. Do not burn the chocolate. Should take no more than 2 minutes. Let cool slightly, then add salt and vanilla. With a hand or stand mixer, mix butter and powdered sugar together. Add chocolate mixture, and mix until smooth and creamy. If needed, add more milk in 1-tbsp increments to smooth out/get to desired texture. Do not ice on cake until the cake is completely cool - it will melt off. Enjoy!